1. Field of the Invention
The present invention relates, in general, to heating cookers and, more particularly, to a heating cooker which evenly heats or cooks food, and is easily cleaned.
2. Description of the Related Art
Japanese Patent Laid-open Publication No. Heisei 8-247473 discloses a conventional heating cooker. In the Japanese heating cooker, a cabinet is fabricated with two casings, that is, an outer casing and an inner casing. The outer casing defines an appearance of the cabinet, while the inner casing, defining a cooking cavity therein, is placed in the outer casing. The cooking cavity is opened at a front thereof, and the opened front of the cooking cavity is closed by a door which is attached by hinges to a lower edge of the cabinet so as to rotate upward to close the cooking cavity and rotate downward to open the cooking cavity. A fan chamber is provided at a rear wall of the cooking cavity by recessing a circular area of the rear wall to a predetermined depth. An air circulation fan and a heater are installed in the fan chamber. The air circulation fan circulates air of the cooking cavity, while the heater heats the air in the fan chamber before the air is distributed to the cooking cavity. A chamber cover is installed at an inlet of the fan chamber so as to cover the circulation fan and heater installed in the fan chamber.
The chamber cover is a circular disc-shaped member with a diameter less than a diameter of the inlet of the fan chamber. Therefore, when the chamber cover is mounted to the inlet of the fan chamber (for example, through a welding process), so as to cover the fan chamber, an annular gap is defined between an outer edge of the chamber cover and an edge of the inlet of the fan chamber. The annular gap acts as an air distribution gap through which the air is distributed from the fan chamber to the cooking cavity. A plurality of air suction ports are provided at a central area of the chamber cover, so that the air is sucked from the cooking cavity into the fan chamber through the air suction ports due to suction force generated by the air circulation fan rotated in the fan chamber. In the fan chamber, the air is forced outward in radial directions of the air circulation fan, and is heated by the heater installed outside a circumference of the air circulation fan, thus becoming hot air. The hot air is, thereafter, distributed from the fan chamber into the cooking cavity through the air distribution gap between the outer edge of the chamber cover and the edge of the inlet of the fan chamber. Food on a rack inside the cooking cavity is thus heated and cooked by the hot air distributed from the fan chamber into the cooking cavity through the air distribution gap.
However, the conventional heating cooker is problematic as follows. That is, the conventional heating cooker is designed such that the hot air, distributed from the fan chamber into the cooking cavity through the air distribution gap provided at the rear wall of the cooking cavity, is forced forward to the food on the rack inside the cooking cavity. The hot air is thus undesirably concentrated to a part of the food, so that the part of the food to which the hot air is concentrated may be excessively cooked or burnt whereas another part of the food may not be desirably cooked. That is, the conventional heating cooker may fail to cook food evenly, and, sometimes, burn a part of the food.
In addition, the air distribution gap of the conventional heating cooker allows foods to enter the fan chamber and contaminate the air circulation fan, heater, and walls of the fan chamber when the food sputters in the cooking cavity during a cooking process. Furthermore, the chamber cover is welded to the inner casing, so that it is impossible for a user to remove the chamber cover from the inner casing or to clean the contaminated interior of the fan chamber.
During a microwave-cooking mode of the conventional heating cooker in which food is cooked by use of microwaves generated by a magnetron, an electromagnetic field is formed at welded junctions between the chamber cover and the rear wall of the cooking cavity. In such a case, sparks occur undesirably at the welded junctions.
Another disadvantage experienced in the conventional heating cooker resides in that the microwaves are introduced from the cooking cavity into the fan chamber through both the air suction ports of the chamber cover and the air distribution gap provided around the chamber cover. Thus, it is necessary to provide a caulked structure at a junction between a motor shaft of the air circulation fan and a shaft bearing provided at a rear part of the fan chamber to prevent leaking of the microwaves from the fan chamber to the atmosphere through the junction. The caulked structure undesirably complicates a rear structure of the cooking cavity, and increases production cost of the heating cooker.